Asparagine residue-specific endoproteases refer to enzymes that split peptide etc. in an amino acid sequence of peptide or protein at the C-terminal side of asparagine residue. Among them, the asparagine residue-specific endoprotease derived from plants is called legumaturain.
Although its enzymatic activity was confirmed in various higher plants, legumaturain was highly purified by no other person than the present inventors since it is very unstable.
Storage proteins of plants are synthesized initially as a prepro-protein, which will not be converted into the form of a mature protein until it is under the action of legumaturain. The storage proteins of plants have no problem on safety and are an excellent source of protein so that there is an earnest demand in food industries to produce it on a large scale.
Accordingly, it is also earnestly demanded to produce on a large scale a highly pure legumaturain that is necessary for the synthesis of the storage proteins.
However, from the reason as described above, it has been very difficult to purif y legumaturain and the demand has never been satisfied yet.